1. Field of the Invention
The present invention relates to a high voltage variable resistor device, and, more particularly, to a high voltage variable resistor device preferably used to adjust the focus voltage and the screen voltage of a television receiver.
2. Description of the Related Art
A high voltage variable resistor device is disclosed in Japanese Unexamined Patent Application Publication No. 9-139302. FIG. 6 is an electrical circuit diagram of a high voltage variable resistor device 101. The high voltage variable resistor device 101 directly receives an input voltage from the output terminal of a flyback transformer FBT for supplying an anode voltage to a cathode-ray tube. A series circuit defined by fixed resistors R13 to R16 and variable resistors VR11 and VR12 is connected between an input terminal THV of the high voltage variable resistor device 101 and a ground. Also, the series circuit of the divided resistors R11 and R12 for voltage detection and a capacitor C are each connected therebetween. A focus voltage is output from an intermediate terminal of variable resistor VR11 for adjusting the focus voltage via a fixed resistor R17, and a screen voltage is output from an intermediate terminal of the variable resistor VR12 for adjusting the screen voltage.
The divided resistors R11 and R12 for voltage detection are provided to detect variations of the anode voltage, and the voltage for detection, which is divided at the connection point of the divided resistors R11 and R12 for voltage detection, is fed back to a high-voltage generation source. The voltage for detection is usually set at about 1/3000 to about 1/2000 of the anode voltage. The capacitor C is a screen correcting capacitor for correcting the distortion of the screen of the television receiver.
The high voltage variable resistor device 101 has a configuration as shown in FIG. 7. That is, a division wall 110a is provided inside an insulation case 110 made of synthetic resin and having one open surface. An insulation substrate 120 on which the variable resistor VR11 for adjusting the focus voltage, the variable resistor VR12 for adjusting the screen voltage, and other suitable components, are provided is bonded and fixed to one of the housing portions. A fixed resistor 160 provided with the divided resistors R11 and R12 for voltage detection is housed and fixed in the other housing portion.
Although not shown, on the surface of the insulation substrate 120, film resistors of the fixed resistors R13 to R17, the variable resistors VR11 for adjusting the focus voltage, and the variable resistors VR12 for adjusting the screen voltage are disposed. In the front section of the insulation case 110 opposing the insulation substrate 120, a rotation shaft having a slider that slides on the film resistor of each of the variable resistor VR11 for adjusting the focus voltage and the variable resistor VR12 for adjusting the screen voltage is axially supported. That is, the variable resistors VR11 and VR12 are defined by the insulation substrate 120, the rotation shaft having a slider, and other suitable components.
As shown in, for example, FIG. 8, in a fixed resistor 160, the divided resistors R11 and R12 for voltage detection defined by film resistors are provided on the surface of an insulation substrate 161. The divided resistor R11 has a meandering pattern and a trimming pattern 162 in the central section thereof. The divided resistor R12 has a wide width pattern, and its entirety is defined by a trimming pattern. When the fixed resistor 160 is manufactured, the voltage for detection is finely adjusted by changing the division ratio by deleting a portion of the trimming pattern 162 of the divided resistor R11 and a portion of the width wide pattern of the divided resistor R12.
However, in the known high voltage variable resistor device 101, since the divided resistors R11 and R12 for voltage detection are provided in the fixed resistor 160, which is another separate body, there is the problem in that the manufacturing cost is high. Furthermore, the number of types of fixed resistors 160 must be increased for each different division ratio of the divided resistors R11 and R12 for voltage detection, and the manufacture management is complex. In addition, the tolerance of the division ratio of the divided resistors R11 and R12 for voltage detection is only up to ±2%, and a strict tolerance is difficult to maintain.